Predictors of Medication Adherence of Patients With Coronary Heart Disease After Percutaneous Coronary Intervention

BACKGROUND: The theory of planned behavior (TPB), combined with social support, forms the extended TPB, which has shown to predict adherence to health-related behavior effectively, but few studies have applied it to explain medication adherence in patients with coronary heart disease (CHD) after percutaneous coronary intervention (PCI). OBJECTIVES: The aim of this study was to explore the factors associated with medication adherence and the underlying mechanisms based on the extended TPB among patients with CHD after PCI. METHODS: A cross-sectional descriptive study was conducted among patients with CHD after PCI in 2 major hospitals in Guangzhou, China. Medication adherence was measured with the Medication Adherence Report Scale. Constructs of the TPB contributing to medication adherence were assessed by the Theory of Planned Behavior Questionnaire for Medication Adherence. Social support was measured by the Multidimensional Scale of Perceived Social Support. Structural equation modeling was used to examine the hypotheses based on the extended TPB. RESULTS: A total of 300 patients were surveyed and 26.0% of them were nonadherent. The structural equation modeling had good fit indices and estimated 62.6% of the variance in medication adherence. Regarding the relationships between the extended TPB constructs and medication adherence, "intention" was directly associated with medication adherence, and "perceived behavioral control" positively predicted medication adherence directly and indirectly. "Affective attitude" and "subjective norm" were indirectly associated with medication adherence through "intention." Social support exerted an indirect effect on medication adherence through "subjective norm." CONCLUSIONS: The extended TPB is an appropriate model to predict medication adherence and provides an effective framework for adherence-enhancing interventions.